This invention relates to a gauge for measuring the pitch of a propeller blade.
Bladed propellers are used in many machines and devices for a myriad of purposes. Examples are the use of a propeller in a fan to blow air or the use of a sturdily constructed propeller to push a boat through water. A typical propeller consists of a plurality of blades mounted on a central hub. The central hub often defines an axial bore by which the hub can be connected to a shaft. Such an axial bore may be substantially circular and have a keyway, for use with a key, or a plurality of splines to engage the shaft.
The blades of such a propeller extend generally radially from the central hub and have a pitch. The pitch is the theoretical distance a propeller would advance longitudinally in one revolution. A means for measuring the pitch of a blade is important as blade pitch is a substantial factor in determining the performance of a propeller. This is particularly important where the blades are adjustable as to pitch.
Several devices exist in the art for measuring the pitch of a propeller blade. The typical device in the prior art consists of a means attachable to the propeller hub with a series of arms and pins to engage the surface of the blade. The pins which engage the blade are connected to slidable or rotatable scales to measure an axial distance and a rotational angle over the axial distance. Alternative devices have protractors mounted upon one of the arms which measure the angle that the pin engages the blade. Other alternative devices use a plurality of pins which are positioned on the blade to, via an arm, give a representation of the blade. Such devices, using movable arms and pins to engage rotational and axial scales are exemplified in Hughey, Jr., U.S. Pat. No. 4,056,888, issued Nov. 8, 1977.
The devices known in the art for measuring the pitch of a propeller blade are generally complicated, difficult to manufacture, expensive and require a great deal of expertise to operate.
It is the object of the present invention to provide a device for measuring the pitch of a propeller blade which has no moving parts.
Another object of the invention is provide a device for measuring the pitch of a propeller blade which is inexpensive and easy to manufacture.
It is another object of the present invention to provide a device for measuring the pitch of a propeller blade which is easy to use and does not require a great deal of expertise on the part of the operator.
A further object of the present invention is to provide a device which can measure the pitch of a propeller blade in a specific sector of the blade.